More
than 250 million years ago, the earth experienced one of the most dramatic
extinction crises, with about 90 percent of Marine life and 70 percent of
terrestrial life disappearing. Exactly what caused so many species to die off
has long been a matter of debate.

Now,
a new study offers important clues. Scientists believe that ocean
acidification, caused by rising levels of carbon dioxide in the air, may have
played a crucial role in the ancient extinction event. Marine life with calcium
carbonate shells, in particular, is particularly vulnerable to acid conditions.

Ocean
acidification refers to the gradual acidification of seawater as the ocean
absorbs excess carbon dioxide from the atmosphere. The term "ocean
acidification" first appeared in the famous British scientific journal
nature in 2003. The oceans currently absorb about 8 billion tons of carbon
dioxide a year, and while it has played an important role in slowing warming,
the oceans have also paid a high price.

As
atmospheric concentrations of carbon dioxide rise over the next few decades,
and the seawater that absorbs the gas eventually becomes more acidic, the earth
is likely to head toward another serious extinction event that could repeat the
history of more than 250 million years ago.

Canada
ocean physicist alvaro monte Montenegro said: "although compared with many
other what is happening, the role of acidification of the oceans, in fact, it
is difficult to quantify, but our results clearly show that ocean acidification
in the ancient extinction events plays a major role, played a great role."

It
is clear that humans have made and will continue to make the oceans more
acidic, and we can expect it to affect some Marine life, of which clams,
mussels and other aquatic shellfish are most at risk. The results suggest that
life may not be able to adapt quickly enough to change the ocean's pH.

PH
is a measure of the activity of hydrogen ions in a solution, which is generally
a measure of the pH of the solution. The higher the pH goes to zero, the more
acidic the solution. And the more we go to 14, the more alkaline the solution
is. At room temperature, a solution with a pH of 7 is neutral.

The
evolution of life is interspersed with many major extinction events, including
the one that wiped out most dinosaurs about 65 million years ago. The sequence
of the most extreme events so far goes back more than 250 million years. The
Permian ~ Triassic extinction event is a mass extinction event that occurred
between the Permian and Mesozoic Triassic about 250 million years ago. In terms
of lost species, 70% of earth's terrestrial vertebrates and up to 96% of all
sea life disappeared. The extinction also caused the only mass extinction of
insects, with 57 percent of "families" and 83 percent of
"genera" disappearing. It took millions of years for the terrestrial
and Marine ecosystems to fully recover, longer than other mass extinctions. PTB
is the largest of five mass extinctions in the geological era, so it's
informally called a "mass extinction," or "mother of mass
extinctions." It took at least 100, 000 years for the ocean to return to
normal after an estimated 450 gigatons of dissolved carbon dioxide were blamed
for an extinction event 65 million years ago.

Scientists
know that giant volcanic eruptions send huge amounts of methane and carbon
dioxide into the atmosphere at very high temperatures. Geological studies have
shown that oxygen levels in parts of the ocean floor are very low, but it's
still not clear what causes it.

In
order to solve some of the mystery, alvaro monte Montenegro and his colleagues
created a computer model, simulation and extinction in before extinction. The
model includes a continent that is precisely aligned according to historical
circumstances, and also the first time the ridg-strewn seafloor has emerged to
create a lifelike pattern of flow circulation. After setting the temperature
and carbon dioxide concentrations to the maximum levels they assumed existed at
the time, the researchers looked at what would happen in the ocean. Their
results confirm that warmer climates do not account for the record of changes
in the oceans at PTB, and that high levels of carbon dioxide alone can cause a
significant drop in the ocean's pH.

British
geologist helwig Noel Paul said: "as for why the extinction of oxygen at
the bottom of the ocean is so little, the model does not provide much evidence,
it shows that we need to do a lot of research work, can we truly understand
occurred in the biggest extinction event in the history of the earth."

But
acidification, or lack of oxygen, is an impending crisis in the modern ocean.
The fossil record shows that the aquatic shellfish were destroyed in PTB because
the acidic environment made it difficult for them to secrete and feed their
shells.

The
severity of the problem has been exacerbated by the cold water, which means
aquatic shellfish in the higher latitudes face the greatest threat today.
According to the researchers' projections, the first casualties could be
pteropods between 2030 and 2050. These snails live in surface waters at high
latitudes, forming the lowest end of many fish and bird food chains. Between
now and 2030, the southern hemisphere's oceans will corrode snails' shells.
These mollusks are an important source of salmon in the Pacific, and if their
populations decline or disappear in some areas, that could affect the salmon
fishing industry. In addition, the loss of coral reefs in the sea's continental
shelf, which generate billions of dollars a year for tourism, will be a major
setback for tourism.

Today's
oceans are more acidic as more carbon dioxide enters the atmosphere through
fossil fuels and other sources and is likely to spread southward into warmer
waters, threatening creatures such as clams, oysters and corals.

Since
the industrial revolution, more than a third of the carbon dioxide released by
human activities has been absorbed by the ocean, increasing the concentration
of hydrogen ions in surface waters by 30 percent over the past 200 years and
lowering pH by 0.1. The increasing acidity of sea water breaks the balance of
Marine chemistry and threatens the Marine ecosystem. Many Marine organisms and
even ecosystems that depend on the stability of chemical environment are faced
with huge threats. The extinction of some shellfish is a strong proof of ocean
acidification. Ocean acidification has also severely damaged biodiversity and
caused the emergence of some invasive species. As the main force of
photosynthesis in the ocean, phytoplankton species are numerous, their
physiological structures are diverse, and their ability to use different forms
of carbon in the sea water is also different. Ocean acidification will change
the conditions of competition among species.

With
so much carbon dioxide being absorbed, the oceans are acidifying at an
unprecedented rate. At present, the only effective solution to the problem is
to reduce carbon dioxide emissions.